1. Field of the Invention
This invention relates to a yarn splicing device for spun yarns.
2. Prior Art
Among various methods of splicing spun yarns, there is a yarn splicing method which utilizes fluid and is advantageous in reduction of occurrence of troubles such as breaks or catches of yarns and so on in succeeding production steps such as knitting, weaving or the like since a joint of yarns obtained by the method do not present a knot compared with a conventional knot such as a fisherman knot or a weaver's knot. In particular, in a pneumatic yarn splicing device which employs air as a fluid, end sections of both yarns to be spliced are put in order in a yarn splicing hole, and overlapping portions of the yarn end sections are acted upon by an air flow to obtain a joint. In this method, however, it is a very effective means for obtaining a good joint to untwist the twist of the yarn end sections in prior to a yarn splicing operation and/or to separate and partially remove fibers adjacent extremities of the yarn end sections to shape each of the extremity portions of the yarn end sections into a tapered configuration.
The present applicant already filed patent applications such as, for example, a Japanese laid-open patent No. 54-7350 (Japanese publication patent No. 56-47108), for a device wherein end sections of yarns are sucked into a yarn end controlling nozzle in which fibers at extremity portions of the yarn end sections are separated from one another whereafter the yarn end sections are placed in order into a yarn splicing nozzle and are acted upon by an injecting air flow to effect intended splicing of the yarns. In this device, the nozzle for untwisting yarn end sections which is called a yarn end controlling nozzle is for use with single yarns and is thus suitable and convenient for untwisting single yarns wherein the peculiar twist provided to the yarns is only one of the Z and S twists. However, there yarns to be spliced are each a ply yarn, they cannot at all be untwisted by the untwisting nozzle of the device.
In particular, in what is called a ply yarn consisting of two or more mutually twisted single yarns, the twist peculiar to the single yarns (hereinafter referred to as "first" twist) and the twist peculiar to the ply yarn (hereinafter referred to as "second twist) consisting of the mutually twisted single yarns are opposite in directions relative to each other, and by this reason, such ply yarns cannot be untwisted by the untwisting nozzle as described above. For example, in case of a ply yarn wherein the first twist is the S twist and the second twist is the Z twist, if an end section of the ply yarn is whirled in one direction, for example, in a direction to untwist the Z twist, the second twist which is the Z twist can be untwisted and hence two single yarns of the ply yarn can be separated from each other, but the S twist provided to the individual single yarns cannot be untwisted successfully. In order to untwist the twist of the single yarns, a whirling flow must be additionally produced in a direction to untwist the S twist. But it is difficult to produce air flows in opposite directions within an untwisting nozzle with an instantaneous time lag one after the other, and even if this should be possible, the arrangement should have to become complicated.